Process of preparing higher fatty aldehydes



Patented Mar. 10, 1936 aosasse roass or rears time. ran e amass 1 Anderson W. lltalstcn and Carey B. Jiacksen, 1w

cage, lilit, assignors to Armour and Company, ilhicago, Ill, a corporation of Illinois No Drawing. Application April 11, 1935,

Serial No. 15,914

is clai (Cl. 260-138) This invention relates to processes of preparing higher aldehydes, such as stearaldehyde, palmitaldehyde, olyaldehyde and others, and it comprises processes wherein a higher fatty acid,

fatty acid aldehydes are important starting ma-' terials for the preparation of compounds now made in other ways. The aldehydic group is extremely reactive and many other new and val- I uable compounds could be made commercially from the higher aldehydes if these substances.

were readily available.

One of the classic ways of converting a higher fatty acid to its corresponding aldehyde includes the step of reacting the calcium salt of the acid with calcium fox-mate. This process however leaves much to be desired; it is costly, yields are poor, and lt-has never come into practical commercial use. In other instances it has been suggested to subject higher fatty acids to pyrolysis but heterogeneous mixtures of reaction products are obtained, from which it is extremely diflicult to separate substantially pure aldehydes. The oxidation of parafflnic hydrocarbons to higher aldehydes is opento similar objections. Regardless of these difliculties, however, any commer ci'ally practical way of making the higher aldehydes is of significant economic interest.

We have now discovered ways by which satisfactory yields of higher aldehydes can be obtained from the corresponding higher fatty acids. We have discovered that vaporized higher fatty acids will react with formaldehyde in the presence of a. catalyst to give significant yields of aldehydes. We have discovered that the reaction is facilitated by the presence of carbon dioxide and steam in the reacting mixture, al-' though these substances need not necessarily be present.

Our process is therefore characterized by vaporizing a higher fatty acid, or its aliphatic esters, and reacting the vaporized substances with gaseous formaldehyde in the presence of a catalyst. We can write the probable reaction as follows, RCOOH being a higher fatty acid.

The actual mechanism of the reaction is doubtless more complex than that given above.

Our invention is applicable to the conversion of numerous higher fatty acids and aliphatic esters-to the corresponding aldehydes. By higher fatty acids, and higher aldehydes, we mean to include those acids and aldehydes having. six or more carbon atoms. Thus, in our process we can start with any of the following higher fatty acids. 'Caprylic, capric, lauric, myristie, palmitic, stearic, arachidic, behenic lignoceric' or carnaubic'cerotic, melissic, oleic, linoleic and linolenic.

Our process is also applicable to the treatment of alkyl esters of any of these acids. Advantageously we start withthe ethyl ester but we can use the propyl, butyl, and other esters. We can also start with the glycerides of these fatty acids. For example we can vaporize stearin or lard and react it with formaldehyde. When starting with the various aliphatic esters specified we believe that'the ester first breaks down or possibly bydrolyzes, to liberate. the free acid. and this in turn is reduced to its corresponding aldehyde. We are not however certain of the actual mechanism of the reaction and content ourselves with noting the observable facts.

We have mentioned the use of catalysts. We find that the reaction is greatly facilitated provided the reaction mixture is brought into contact with a catalyst. Advantageously these catalysts are of an oxidizing nature and are best chosen from the metal oxides of the elements of the fifth and sixth group of the periodic table. These are generally oxides of vanadium, chromium, and molybdenum. Advantageously we also use manganese oxide this being an oxidizing metal oxide catalyst of the seventh group. Of the various oxides available we have obtained the best resuits by using a catalyst composed of a mixture aldehyde, 1,200 parts by weight of steam and 50 parts by weight of carbon dioxide over an MnO.VzOa catalyst maintained at about 400 C. Product flowing from the reaction zone is condensed to give aqueous and oily layers. The oily layer amounts to about 970 parts of greenish oilylike liquid. Fractionation of it gives the following fractions:

Fraction 1-B. P. -190 C. at 5 mm.--

about 490 parts Fraction 2-B. P. 190-205 C. at 5 mm.-

about 142 parts Fraction 3-B. P. above 205 C.

about 338 parts Fraction 1 is essentially olyl aldehyde and small amounts of lowermolecular weight aldehydes. Fraction 2 is mainly unchanged oleic acid. Fraction 3 is oleic acid with small amounts of ketones. All parts in the above example are by weight and the rate of flow is of the order of about 100 parts of acid per hour. This, of course, is variable and depends upon the capacity of the apparatus. We can recycle unchanged oleic acid to the reaction zone but we find it best to free the unchanged oleic acid from any small amounts of high molecular weight ketones, as by fractionation, to prevent contamination of the catalyst.

The presence of water vapor is desirable because it appears to prevent any substantial decomposition or cracking of the higher fatty acids. We do not believe that it enters into the actual a dehyde-forming process but that it tends to stabilize the reaction mixture against undesirable side reactions.

In a similar way we can vaporize any of the higher fatty acids listed above, and pass the vapors together with formaldehyde to the heated catalyst. In some cases we steam-distill the fatty acid and pass the resulting steam-fatty and vapor mixture directly to the reaction zone. This is an advantageous procedure when starting with very high boiling fatty acids or those which show some tendency to decompose when heated to the boiling point.

We can also operate under moderate pressure below atmospheric, of the order of five pounds per square inch, but the only pronounced effect of this is to facilitate the vaporization of the fatty acid.

a In another example we start with ethyl stearate, one of the esters specifically mentioned above, and pass a mixture of about 1,000 parts by weight of the ester, 600 parts by weight of formaldehyde and 1,200 parts by weight of steam over a manganese oxide catalyst heated to about 400 C.

This gives us an oily condensate amounting to about 960 parts which, on distillation, gives the following fractions:

Fraction 1-B. P. 100-180 0. at 5 mm.-

about 360 parts Fraction 2--B. P. 180-190 C. at 5 mm.-

about 210 parts Fraction 3-B. P. 238 C. at 5 mm.

about 280 parts Residue-B. P. above 238 C. at 5 m m.--

about 110 parts Fraction 1 consists essentially of stearaldehyde or lower aldehydes. .Fraction 2 contains stearaldehyde together with unchanged ethyl stearate. Fraction 3 is composed essentially of ethyl stearate and stearic acid. The residue is higher ketones and some stearic acid.

when starting with stearic acid itself the products obtained are about the same. This leads us to conclude that some hydrolysis of the ester first occurs and then the resulting free stearic acid reacts with the formaldehyde. In both of the above examples we do-of course obtain an aqueous condensate as well as the oily layer for which fractionation data is given above. This aqueous condensate comprises most of the steam introduced together with some ethyl alcohol when ethyl stearate is used as a starting material.

In the case of ethyl stearate we find that we need not add carbon dioxide to the reaction mixture but small quantities of it can be introduced. Apparently the carbon dioxide helps to prevent decomposition of the fatty acid to ketonic byproducts and this is particularly noticeable when starting with unsaturated fatty acids such as oleic.

In a further example we start with higher fatty acid mixtures collectively known as lard fatty acids. Lard is a cheap-and abundant material and its fatty acids can be obtained therefrom inexpensively. When starting with mixtures of.

fatty acidswe obtain a reaction product containing mixed higher aldehydes. For most commercial uses we need not separate individual aldehydes therefrom. We can reduce the mixture to the corresponding higher alcohols to give products useful when sulfonated or sulfated, as wetting out" agents. In a similar fashion we can start with lard itself and also with other glycer- -ides of the higher fatty acids.

In the above examples we have referred to temperatures of about 400 C. We are not to be liniited however to this specific temperature. Ad-

va-ntageously the temperature ranges from the boiling point of the higher fatty acid substances up to about 600 C. For the higher fatty acids used in our process this means a temperature range ofa minimum of about 250 C. to a maximum of about 600 C. The specific temperature is therefore largely determined by the character of the starting material and is adequately defined in the appended claims by specifying that the higher fatty acid substances are vaporized.

Although we have specifically referred to the use of formaldehyde we can of course use substances which liberate formaldehyde at the reaction temperatures. Meta and para formaldehyde have this property and can be used since at elevated temperatures they decompose to liberate formaldehyde. Therefore, although they can be used, we find it much more advantageous to begin with an ordinary aqueous solution of commercial formaldehyde.-

Since the catalysts used in our process are of an oxidizing character we so define them broadly in the appended claims.

Having thus described our invention claim is.

l. The process of preparing higher aldehydes which includes reacting a vaporized higher fatty acid substance chosen from the group consisting ofhigher fatty acids and their aliphatic esters with formaldehyde vapor in the presence of an oxidizing catalyst. 2. The process of preparing higher aldehydes which includes reacting a vaporized higher fatty acid substance chosen from the group consisting of higher fatty acids and their aliphatic esters with formaldehyde vapor in the presence of an oxidizing catalyst and water vapor.

3. The process of preparing higher aldehydes which includes reacting a vaporized higher fatty acid substance chosen from the group consisting what we of higher fatty acids and their aliphatic esters withformaldehyde vapor in the presence of an oxidizing catalyst, water vapor and carbon di-,

' includes reacting a vaporized oleic acid substance chosen from the group consisting of oleic acid and its aliphatic esters with formaldehyde vapor in the. presence of an oxidizing catalyst.

6. The process of preparing higher aldehydes which includes reacting a vaporized alkyl ester of a higher fatty acid with formaldehyde vapor 'in the presence of an oxidizing'catalyst.

7. The process of preparing higher aldehydes which includes reacting a vaporized higher fatty acid substance chosen from the group consisting of higher fatty acids and their aliphatic esters with formaldehyde vapor in the presence of an oxidizing catalyst at a temperature of about 8. The process. of preparing higher aldehydes which includes reacting a vaporized higher fatty acid substance chosen from the group consisting of higher fatty acids and their aliphatic esters -with formaldehydevapor in the presence of an oxidizing catalyst and water vapor at a temperature of about 400 C. 1

- 9. The process as in claim '3 wherein the temperature isabout 400 C.

10. The process which includes reacting a vaporized higher fatty acid substance chosen from p 3 the group consistihg of higher fatty acids and their aliphatic esters with formaldehyde vapor in the presence of a vanadium oxide catalyst.

11. The process of preparing higher aldehydes which includes reacting avaporized higher fatty acid substance chosen from' the group consisting of higher fatty acids and their aliphatic esters with formaldehyde vapor in the presence of a vanadium oxide catalyst and water vapor.

12. The process of preparing higher aldehydes which includes reacting a vaporized higher fatty acid substance chosen from the group consisting of higher fatty acids andtheir aliphatic esters with formaldehyde vapor in the presence of a vanadium oxide catalyst, water vapor and carbon' dioxide.

13. The process of preparing higher aldehydes 'which includes reacting of vaporized higherfatty acid with formaldehyde vapor in the presence of a vanadium oxide catalyst.

14. The process of preparing higher aldehydes which comprise reacting a vaporized alkyl ester of a higher fatty acid with formaldehyde vapor in the presence of a vanadium oxide catalyst.

15. The process of preparing higher aldehydes which comprise reacting a vaporized higher fatty acid with formaldehyde vapor in the presence of a'vanadium oxide catalyst at a temperature of about 400 C.

16. The process of preparing higher aldehydes which comprise reacting a vaporized alkyl ester of a higher fatty acid with formaldehyde vapor in the presence of a vanadium oxide catalyst at a temperature of about 400 C.

ANDERSON W. RALSTON. CAREY B. JACKSON. 

